A Novel Role for Copper in Ras/Mitogen-Activated Protein Kinase Signaling

Abstract

Copper (Cu) is essential for development and proliferation, yet the cellular requirements for Cu in these processes are not well defined. We report that Cu plays an unanticipated role in the mitogen-activated protein (MAP) kinase pathway. Ablation of the Ctr1 high-affinity Cu transporter in flies and mouse cells, mutation of Ctr1, and Cu chelators all reduce the ability of the MAP kinase kinase Mek1 to phosphorylate the MAP kinase Erk. Moreover, mice bearing a cardiac-tissue-specific knockout of Ctr1 are deficient in Erk phosphorylation in cardiac tissue. in vitro investigations reveal that recombinant Mek1 binds two Cu atoms with high affinity and that Cu enhances Mek1 phosphorylation of Erk in a dose-dependent fashion. Coimmunoprecipitation experiments suggest that Cu is important for promoting the Mek1-Erk physical interaction that precedes the phosphorylation of Erk by Mek1. These results demonstrate a role for Ctr1 and Cu in activating a pathway well known to play a key role in normal physiology and in cancer.

ACKNOWLEDGMENTS

The Phantom Gal4, UAS mCD8::GFP/TM6, Tb flies were provided by M. O'Connor (University of Minnesota), and plasmid pCMV-HA-Mek1 was provided by A. Catling (LSU Health Science Center). We thank Eric Spana for expert advice on Drosophila experiments and Jamie Roebuck for Drosophila embryo injections at the Duke University Model Systems Genomics Core Facility.

We gratefully acknowledge funding support from an American Heart Association postdoctoral fellowship to B.-E. Kim (09POST2251047) and National Institutes of Health grants DK074192 to D.J.T., CA123031 to C.M.C., and GM083292 to D.R.W. M.L.T. was a Ph.D. student in the NIH-funded Duke University Program in Genetics and Genomics. H.K. was supported by training grant T32 NIH DK07115. D.C.B. was supported by training grant T32 NIH CA059365-14.